A wireless communication system, such as a mobile communication system using a Long Term Evolution (LTE) specification, has been moving to a flatter, all-IP architecture in which base stations (BSs) are directly, or indirectly, connected to a packet core network (CN) through some gateways (GWs). There is a trend that small cells, such as femtocells in the LTE system, are increasingly deployed for supporting communications with more user equipments (UEs) per unit area. Due to the high density of small cells located in a given area, it is typical that a GW is connected with hundreds or thousands of small cells.
Paging is a procedure of locating a UE in a wireless communication system. It usually generates a significant amount of paging traffic on the links between the GW and the BSs due to the large number of BSs as well as the large number of potential UEs to be paged. Note that the links are usually implemented as part of an Internet Protocol (IP) network. It is desirable if the amount of paging traffic can be reduced.
In the art, techniques for reducing the amount of paging traffic usually employ one the following two approaches: limiting the number of cells or BSs to do paging to thereby limit the paging traffic; and deciding whether or not to page a target UE.
Techniques based on limiting the number of cells or BSs to do paging include the following. U.S. Pat. No. 8,428,625 suggests a technique that first pages a subset of the total number of cell sites in a tracking area (TA) and then expands the subset after unsuccessful attempts to page a UE. In U.S. Pat. No. 6,351,641, a method for re-paging is disclosed. An area according to the location information is divided into a number of sub-areas. If re-paging is required, the number of re-pagings to be performed in each cell within the area is limited based on a limitation value. In WO2014057101, a permanent user identity is used to determine a set of small cells to page a UE based on a small cell last visited by the UE and small cells that are neighbors of the last-visited small cell. US2015249969 discloses a GW device that stores information regarding an environment around a BS and that selects the cells to be paged for an UE based on the stored information. In EP2254378, a method is provided for a GW to page a UE that is in idle mode and resides within a cluster of femtocells. The GW determines whether which femtocells to be involved in paging according to a UE identifier and an identity of at least one femtocell that the UE previously visited. US20140370922 suggests using a table to map a UE and a candidate BS that has some likelihood of successfully paging the UE, thereby some paging traffic can be saved by focusing on this candidate BS in paging.
Techniques based on deciding whether or not to page a target UE include the following. U.S. Pat. No. 8,537,829 suggests that paging may not be needed by determining if a bearer connection or link is in the process of being established, thereby enabling a reduction of paging traffic for the system. In US20100124223, a GW having intelligence to determine whether or not to page a particular UE is disclosed. The GW determines to page the UE when the UE is in an idle state or when one or more selective paging rules are satisfied. In WO2011026663, a method for determining whether or not to page a UE is suggested, based on a bearer identification and a framework table comprising a number of selection criteria entries for BS name, quality of service class indicator, etc.
Furthermore, WO2001080588 suggests a system using multicasting to transmit paging requests from a GW to a plurality of BSs for optimizing paging efficiency. Nonetheless, the use of multicasting is not compliant to major wireless communication standards such as the LTE specification.
It is advantageous to have a technique for reducing paging traffic based on a new approach different from the aforementioned two approaches while maintaining compliance with major wireless communication standards, such that a greater potential in reducing paging traffic is realizable in practice. There is a need in the art for such technique.